1. Field of the Invention
The present invention relates to a method of manufacturing an Nb.sub.3 Sn superconducting wire having an excellent superconducting property.
2. Description of the Related Art
In the manufacture of Nb.sub.3 Sn superconducting wires, since an Nb.sub.3 Sn compound is brittle, methods, e.g., a composite processing method, an internal Sn method, and a tube method of basically producing an Nb.sub.3 Sn phase in the final stage have been developed.
In the composite processing method of the methods described above, as shown in FIG. 1A, a through hole is formed in a Cu-Sn-based alloy billet 1. An Nb rod 2 is inserted in this through hole to form a composite billet 3. This composite billet 3 is subjected to drawing to form a composite wire 5. At this time, a bronze layer 4 constituted by a Cu-Sn-based alloy covers the circumferential surface of the Nb rod 2, as shown in FIG. 1B. Finally, the composite wire 5 is subjected to a predetermined heating process to diffuse Sn in the bronze layer 4 to the Nb rod 2, so that an Nb.sub.3 Sn phase 6 is produced at the interface between the bronze layer 4 and the Nb rod 2, thus obtaining an Nb3Sn superconducting wire 7 as shown in FIG. 1C. The superconducting wire obtained in this method is electromagnetically stable as the Nb.sub.3 Sn phase is composed in the bronze layer. Therefore, this superconducting wire is advantageous in that it can be magnetized quickly, and is thus widely used in practice.
However, the Sn content in the Cu-Sn-based alloy billet used in the above composite processing method is controlled to an amount within a range of a solid solution in Cu considering the workability, that is, the Sn content is controlled not to exceed 15.1 wt %. As a result, the amount of produced Nb.sub.3 Sn phase is limited and a good superconducting property such as a high critical current density (Jc) cannot be obtained.